Sudden cardiac death kills 300,000 people in the United States yearly. More than half of these deaths are caused by arrhythmias including ventricular tachycardia. Radiofrequency ablation, which successfully treats supraventricular tachycardia, is not successful at treating ventricular tachycardia because conventional RF ablation catheters cannot treat a large enough volume of myocardium. In Phase 1 of this project, we have demonstrated the feasibility of saline-enhanced ablation. We will have used infusion of warm saline through the myocardium (simultaneous with the application of radiofrequency or laser heating energy) to increase the tissue thermal transport by a factor of 20 or more. We have shown that this method can increase the volume of thermal lesions in myocardium by a factor of 12. These lesions are capable of treating the full thickness of the myocardium, and therefore show promise toward treatment of ventricular tachycardia. We will continue the development of this system during this Phase 2 project. Based on the Phase 1 results we will continue our development using saline enhanced radiofrequency ablations. We will develop a steerable catheter that will have a porous radiofrequency electrode at the tip, which will be inserted into the myocardium. The catheter will have a central lumen with an RF heater to heat the saline before injecting it into the myocardiurn. We will qualify this prototype catheter and system in preclinical studies of ventricular tachycardia in animal models at the Mayo Clinic and the Brigham and Women's Hospital.